Method for making carboxy-functionalized polyphenylene ethers, and blends containing them

ABSTRACT

Carboxy-functionalized polyphenylene ethers containing structural units with a carboxyalkyl group in the 2-position are prepared by redistribution of a polyphenylene ether with a 2-carboxyalkylphenol such as 2-(3-carboxypropyl)phenol (melilotic acid), or by oxidative coupling of a suitable phenol with such a 2-carboxyalkylphenol. The products form compatibilizing copolymers with polymers containing carboxylic acid-reactive functional groups, such as polyesters, polyamides and epoxy resins.

This application is a division of application Ser. No. 09/426,474, filedOct. 26, 1999, now U.S. Pat. No. 6,268,463, which is a division of Ser.No. 09/096,149 filed Jun. 11, 1998, now U.S. Pat. No. 6,063,875, whichis hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to polyphenylene ethers, and more particularly tofunctionalized polyphenylene ethers useful for the compatibilization ofcopolymer blends.

Polyphenylene ethers are a widely used class of thermoplasticengineering resins characterized by excellent properties includinghydrolytic stability, dimensional stability, toughness, heat resistanceand dielectric properties. It is of continuing interest to introducethese desirable properties into polymer blends by incorporating thepolyphenylene ethers as blend constituents. This is often difficult,however, since the polyphenylene ethers are incompatible with many otherpolymers.

A strategy frequently used to compatibilize polyphenylene ethers withother polymers is to introduce into the polyphenylene ether functionalgroups which are reactive with said other polymers, enabling theformation of copolymer-containing compositions in which the copolymersserve as compatibilizers. For example, polyphenylene ethers containingcarboxylic acid functional groups or derivatives thereof can formcopolymers with such other polymers as polyamides, hydroxy-terminatedpolyesters and epoxy group-containing polymers.

Carboxy or carboxy-derived groups (e.g., anhydride groups) have beenintroduced into polyphenylene ethers by reaction through the hydroxy endgroups with such compounds as trimellitic anhydride acid chloride, bygrafting reactions with such compounds as maleic anhydride or fumaricacid, and by redistribution with acidic compounds such asp-hydroxyphenylacetic acid. Redistribution reactions are often ofparticular interest since they may be conducted under relatively mildconditions, typically including temperatures not substantially greaterthan 100° C. and the presence of non-destructive catalysts such asdiaryl peroxides and quinones and relatively inert solvents such astoluene. The redistribution reaction results in a breakup of polymermolecules into lower molecular weight molecules containing the desiredcarboxylic acid or other functional groups.

Redistribution with the aforementioned acidic compounds is somewhatdifficult, however, since said compounds are not adequately soluble insolvents such as toluene. Moreover, the mechanism of the redistributionreaction is such that only low levels of such compounds can beincorporated in the polyphenylene ether, owing in part to substitutionin the para position which makes that position unavailable for reaction.

U.S. Pat. No. 5,880,221 discloses attempts at redistribution ofpolyphenylene ethers with various aryl-substituted alkanoic acids. Itwas found that whereas carboxy phenols bearing two phenolic hydroxylgroups and alkyl substituents ortho to the phenolic hydroxy groups, suchas 4,4-bis(3,5-dimethyl-4-hydroxyphenyl)pentanoic acid, did incorporate,simple phenols such as p-hydroxyphenyloctanoic acid did not. Interestcontinues, therefore, in the development of improved functionalizationstrategies employing other carboxylic acids, especially those of simplermolecular structure than the aforementioned bisphenolic acid.

Japanese Kokai 5/59,270 and 5/59,272 disclose reaction products ofepoxy- and carboxy-functionalized olefin polymers with copolyphenyleneethers in which a portion of the structural units contain a —(CH₂)₃OHgroup. Said copolyphenylene ethers are produced by copolymerization viaoxidative coupling of two phenols, one containing and one not containingsaid group. There is no disclosure of a copolyphenylene ether containinga carboxyalkyl group.

SUMMARY OF THE INVENTION

The present invention is based on the discovery that certaino-hydroxyaromatic-substituted aliphatic carboxylic acids are capable ofincorporation under mild conditions into polyphenylene ethers, either bycopolymerization or by redistribution. The conditions employed includeuse of a single solvent in which the polyphenylene ether has highsolubility.

One aspect of the invention, therefore, is carboxy-functionalizedpolyphenylene ethers comprising structural units of the formulas

wherein each Q¹ is independently halogen, primary or secondary loweralkyl, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; each Q² and Q³ is independently hydrogen,halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹; and R is analkylene radical containing at least 1 carbon atom.

A further aspect of the invention is a method for preparation of suchfunctionalized polyphenylene ethers which comprises redistributing apolyphenylene ether with a 2-carboxyalkylphenol of appropriate formula(corresponding to formula II) in the presence of a redistributioncatalyst.

Another aspect of the invention is a method for production of suchfunctionalized polyphenylene ethers which comprises oxidatively couplingat least one monohydroxyaromatic compound with said2-carboxyalkyiphenol.

These carboxy-functionalized polyphenylene ethers are reactive andreadily form copolymers with other reactive polymers. Therefore, a stillfurther aspect of the invention is resinous compositions comprisingcopolymers of said functionalized polyphenylene ethers with at least onepolymer containing carboxylic acid-reactive functional groups.

DETAILED DESCRIPTION; PREFERRED EMBODIMENTS

The polyphenylene ethers which are functionalized according to theinvention are known polymers having structural units of formula I. Bothhomopolymer and copolymer polyphenylene ethers are included. Thepreferred homopolymers are those containing 2,6-dimethyl-1,4-phenyleneether units. Suitable copolymers include random copolymers containingsuch units in combination with (for example)2,3,6-trimethyl-1,4-phenylene ether units. Also included arepolyphenylene ethers containing moieties prepared by grafting onto thepolyphenylene ether in known manner such materials as vinyl monomers orpolymers such as polystyrenes and elastomers, as well as coupledpolyphenylene ethers in which coupling agents such as low molecularweight polycarbonates, quinones, heterocycles and formals undergoreaction in known manner with the hydroxy groups of two polyphenyleneether chains to produce a higher molecular weight polymer, provided asubstantial proportion of free OH groups remains.

The polyphenylene ethers generally have an intrinsic viscosity greaterthan about 0.25, most often in the range of about 0.25-0.6 andespecially 0.4-0.6 dl./g., as measured in chloroform at 25° C.

The polyphenylene ethers are typically prepared by the oxidativecoupling of at least one monohydroxyaromatic compound such as2,6-xylenol or 2,3,6-trimethylphenol. Catalyst systems are generallyemployed for such coupling; they typically contain at least one heavymetal compound such as a copper, manganese or cobalt compound, usuallyin combination with various other materials.

Particularly useful polyphenylene ethers for many purposes are thosewhich comprise molecules having at least one aminoalkyl-containing endgroup. The aminoalkyl radical is covalently bound to a carbon atomlocated in an ortho position to the hydroxy group. Products containingsuch end groups may be obtained by incorporating an appropriate primaryor secondary monoamine such as di-n-butylamine or dimethylamine as oneof the constituents of the oxidative coupling reaction mixture. Alsofrequently present are 4-hydroxybiphenyl end groups and/or biphenylstructural units, typically obtained from reaction mixtures in which aby-product diphenoquinone is present, especially in acopper-halide-secondary or tertiary amine system. A substantialproportion of the polymer molecules, typically constituting as much asabout 90% by weight of the polymer, may contain at least one of saidaminoalkyl-containing and 4-hydroxybiphenyl end groups.

It will be apparent to those skilled in the art from the foregoing thatthe polyphenylene ethers contemplated for use in the present inventioninclude all those presently known, irrespective of variations instructural units or ancillary chemical features.

The functionalized polyphenylene ethers of the invention contain, inaddition to structural units of formula I, those of formula II in whichQ¹⁻³ are as previously defined. The units of formula II arecharacterized by a carboxyalkyl group in the 2- or 3-position,preferably the 2-position, relative to the oxygen atom and a Q² moietyin the other of the 2- and 3-positions. The R radical in saidcarboxyalkyl group is an alkylene radical containing at least 1 andpreferably 2-6 carbon atoms; it may be linear or branched and is usuallylinear. Particularly preferred is the ethylene radical, whereupon thecorresponding carboxylic acid is 2-(3-carboxypropyl)phenol (meliloticacid).

The first method of the invention for preparation of the functionalizedpolyphenylene ethers is by redistribution of a conventionalpolyphenylene ether with the appropriate 2-carboxyalkylphenol; i.e., thecompound corresponding to formula II (hereinafter sometimes simply“acid” for brevity). Redistribution may be effected as described, forexample, in U.S. Pat. Nos. 3,367,978, 4,234,706 and 5,213,886 and inWhite et al. J. Org. Chem., 34, 297-303 (1969), the disclosures of whichare incorporated by reference herein.

The redistribution reaction typically involves heating the polyphenyleneether in solution in a relatively inert solvent, most often an aromatichydrocarbon such as toluene or xylene, with the acid and aredistribution catalyst at a temperature in the range of about 50-110°C. Suitable redistribution catalysts include peroxides such as benzoylperoxide, cumyl peroxide, t-butylperbenzoic and t-butylalkanoic acidsand quinones such as 3,3′,5,5′-tetramethyl-4,4′-diphenoquinone (TMDQ).

Redistribution is accompanied by cleavage of the polymer molecule by theacid, which is incorporated in the cleaved molecules, most often as anend group at the head of the molecule. The proportion of acid isdetermined by the degree of functionalization desired coupled with theoverall molecular weight desired in the product; high proportions ofacid result in a high degree of functionalization and a lower averagepolymer molecular weight, while low proportions afford a highermolecular weight polymer with a low degree of functionalization. Ingeneral, acid levels are in the range of about 1-10% and preferablyabout 2-5% by weight based on polyphenylene ether. The promoter is mostoften employed in the amount of about 1-10% by weight based onpolyphenylene ether.

The second preparative method of the invention is copolymerization ofthe acid in suitable proportions with at least one monohydroxyaromaticcompound, i.e., the one corresponding to formula I, in an oxidativecoupling reaction. The conditions of said reaction are theart-recognized ones, typically including the presence of a catalyst ofoxidative coupling as previously described. An advantage of this methodof preparation may be the ease of preparing functionalized polyphenyleneethers of relatively high molecular weights.

The resinous compositions of the invention may be prepared by effectingreaction between the carboxy-functionalized polyphenylene ether and anypolymer containing one or more functional groups which are reactive withcarboxylic acids. Illustrative groups of this type are hydroxy, aminoand epoxy groups. Said polymer may be thermoplastic or thermosetting.Examples of suitable polymers are hydroxy-terminated polyesters,amine-terminated polyamides, and epoxy resins including glycidyl ethersof bisphenols, epoxy-functionalized olefin polymers, epoxy novolaks andalicylic epoxy resins.

The reaction of the polymer with the carboxy-functionalizedpolyphenylene ether may take place under any suitable conditions,including solution and melt reaction conditions. Where appropriate, theymay be conducted in the presence of suitable catalysts, as illustratedby phase transfer catalysts and epoxy cure catalysts. Other materials,both reactive and non-reactive, may be present. Illustrative materialsare impact modifiers, hardeners, fillers, pigments and stabilizers.

The invention is illustrated by the following examples. All parts andpercentages are by weight. Molecular weights are weight average unlessotherwise indicated and were determined by gel permeationchromatography. Inherent viscosities were determined in chloroform at25° C. Carboxy incorporation was determined by proton nuclear magneticresonance spectroscopy.

EXAMPLES 1-4

Samples (20 g each) of a poly(2,6-dimethyl-1,4-phenylene ether) having aweight average molecular weight of about 50,100 and an inherentviscosity of 0.40 dl/g and 800 mg of melilotic acid were dissolved in100 ml of toluene. Various amounts of benzoyl peroxide were added andthe mixtures were heated at 90° C. for 90 minutes. They were then cooledand the functionalized polyphenylene ethers were precipitated byaddition of methanol, filtered and dried overnight in vacuum. Theresults are given in Table I.

TABLE I Example 1 2 3 4 Benzoyl peroxide, g 0.40 0.80 1.20 1.60 ProductMw 18,900 16,000 13,700 12,200 Product Mn  6,400  5,400  3,300  3,000Carboxy content, μmol/g 106 123 140 146 Carboxy incorporation, % 44 5158 61

EXAMPLES 5-7

The procedure of Examples 1-4 was repeated, substituting TMDQ for thebenzoyl peroxide. The results are given in Table II.

TABLE II Example 5 6 7 TMDQ, g 0.20 1.20 1.60 Product Mw 16,100 11,60011,700 Product Mn  4,300  3,500  3,300 Carboxy content, μmol/g 117 161154 Carboxy incorporation, % 49 67 64

EXAMPLE 8

A 50% solids solution in toluene was prepared from 31 parts of thecarboxy-functionalized polyphenylene ether of Example 2, 37.8 parts of atetrabromobisphenol A diglycidyl ether sold by Dow Chemical under theproduct designation “DER 542”, 17.6 parts of a copolymer of bisphenol Aand tetrabromobisphenol A diglycidyl ether, 17.6 parts of an epoxynovolak sold by Ciba Geigy under the product designation “EPN 1138”,3.64 parts of zinc octanoate, 0.33 part of 2-ethyl-4-methylimidazole and0.84 part of diaminodiethyltoluene. A 7628 E-style glass fiber fabricwas impregnated with the solution and the impregnated fabric was heatedat 150° C. for 7 minutes to remove solvent and partially cure the epoxyresins. Six plies of the resulting reinforced prepreg were layered andheated in a compression mold at 200° C. for 3 hours. The product was alaminate having the following properties:

Resin content - 27.08%; Solvent resistance (methylene chloride) - good;Tg - 190° C.; Dielectric constant - 4.7; Dissipation factor - 0.0061;Flammability (UL-94) - V-0.

What is claimed is:
 1. A method for preparing a functionalizedpolyphenylene ether comprising structural units of the formulas

wherein each Q¹ is independently halogen, primary or secondary loweralkyl, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; each Q² and Q³ is independently hydrogen,halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹; and R isethylene, which comprises redistributing a polyphenylene ether withmelilotic acid in the presence of a redistribution catalyst.
 2. A methodaccording to claim 1 wherein the redistribution catalyst is a peroxideor a diphenoquinone.
 3. A method according to claim 2 wherein theredistribution catalyst is benzoyl peroxide.
 4. A method according toclaim 2 wherein the redistribution catalyst is3,3′,5,5′-tetramethyl-4,4′-diphenoquinone.
 5. A method according toclaim 2 wherein the redistribution temperature is in the range of about50-110° C.
 6. A method according to claim 1 wherein each Q¹ is methyland each Q² is hydrogen.
 7. A method according to claim 6 wherein eachQ³ is hydrogen.
 8. A method for preparing a functionalized polyphenyleneether comprising structural units of the formulas

wherein each Q¹ is methyl; each Q² and Q³ is hydrogen, which comprisesredistributing a polyphenylene ether with melilotic acid in the presenceof a redistribution catalyst selected from the group consisting of aperoxide, benzoyl peroxide, a diphenoquinone, and3,3,5,5′-tetramethyl-4,4′-diphenoquinone.